It was an oral tradition. Recitation was how it was passed on before it was finally written down. You see the echoes of this in a lot of early Greek writing, they contain a large amount of quotes out of Homer. Being able to navigate this maze of "Darmok and Jalad"-speak with Homer quotes meant you were well educated.

Only thing I've found that comes close is some of Augustine's writing. He does the same with Bible quotes in his Confessions.